The development and function of the Drosophila nervous system will be studied, through experiments involving the genetics of acetylcholine (ACh) metabolism. We have isolated mutants (Ace-lethals) which eliminate activity for acetylcholinesterase (AChE), the enzyme which degrades this neurotransmitter of the central nervous system (CNS). Most such mutants are lethal by late embryonic-early larval stages (and have no AChE activity then) except that (1) AChE-null tissues can survive in certain portions of the nervous system, in genetic mosaics and (2) certain combinations of Ace-lethals are temperature-sensitive (ts), allowing survival to adulthood at one temperature but not another. We will use these mutants to map foci for Ace-induced lethality, and use the conditional alleles to determined ts periods for lethality. We will probe the function of the CNS, as controlled by cholinergic synapses, by monitoring physiological and behavioral defects influenced by Ace mutations, in mosaic adults and in Ace ts-bearing adults exposed to non-permissive conditions. The Ace mutations will also be used in biochemical experiments designed to analyze the nature of the AChE molecule in this organism. For further investigation of CNS development as influenced by ACh metabolism, we propose to isolate mutations in the gene coding for choline acetyl-transferase (CAT), the ACh-synthetic enzyme. Through genetic techniques of "segmental aneuploidy," we have discovered one very small segment of chromosome 3 (distinct from the Ace locus, which is also on that chromosome), a duplication of which increases CAT activity, and a deletion of which decreases it. The deletion will be used to induce CAT-null alleles--some of which will hopefully be ts lethals--which can then be used in experiments analogous to those proposed in regard to the Ace mutants. In addition, we would be able to eliminate the presence of the neurotransmitter--in various CNS tissues (in mosaics) and at certain times, and ask critically if ACh is specifically involved in controlling particular kinds of interneuronal connectivity in the development of the nervous system.